class_docstr: Base class for 3D cameras supporting orthographic and
  perspective projections.
  
  Parameters
  ----------
  fov : float
      Field of view. Default 60.0.
  scale_factor : scalar
      A measure for the scale/range of the scene that the camera
      should show. The exact meaning differs per camera type.
  **kwargs : dict
      Keyword arguments to pass to `BaseCamera`.
docstr: The measure for the scale or range that the camera should cover
  
  For the PanZoomCamera and TurnTableCamera this translates to
  zooming: set to smaller values to zoom in.
docstr_tok: ["The","measure","for","the","scale","or","range","that","the","camera","should","cover","For","the","PanZoomCamera","and","TurnTableCamera","this","translates","to","zooming",":","set","to","smaller","values","to","zoom","in","."]
code: def scale_factor(self):
      """The measure for the scale or range that the camera should cover
  
      For the PanZoomCamera and TurnTableCamera this translates to
      zooming: set to smaller values to zoom in.
      """
      return self._scale_factor
  
imports: from __future__ import division
  import math
  import numpy
  from .base_camera import BaseCamera
  from ...util import keys, transforms
  from ...visuals.transforms import MatrixTransform
label_desc: Use image node_id 3 for calling the PerspectiveCamera obj's underlying member method code with example usage: obj.scale_factor() and returns: self